#在users表中查询注册时间最早的十条会员信息。
sql = select * from user order by cdate asc limit 10;

#从两个表中查询点赞数最高的5条博客信息，要求显示字段：（博文id，标题，点赞数，会员名)
sql = select blog.id, user.name,blog.title,blog.pcount from user ,blog where blog.uid = user.id order by pcount DESC limit 5;

#统计每个会员的发表博文数量（降序），要求显示字段（会员id号，姓名，博文数量）
sql = select user.id, user.name, count(blog.uid) from user, blog where user.id = blog.uid group by blog.uid order by count(blog.uid) desc;

#获取会员的博文平均点赞数量最高的三位。显示字段（会员id，姓名，平均点赞数）
sql = select user.id,user.name, AVG(blog.pcount) from user,blog where user.id =blog.uid group by blog.uid order by AVG(blog.pcount) desc limit 3;

#删除没有发表博文的所有会员信息
sql = delete from user where id not in (select uid from blog);

